Apple should be expanding its use of sapphire to home buttons for the iPad and iPad mini, say sources in the Taiwanese sapphire industry. Sapphire is already used in the camera lenses and home button/Touch ID sensor for the iPhone 5s. If Apple is indeed planning to bring sapphire to iPad buttons, that may imply that Touch ID technology will follow.

It's further suggested that Apple could adopt sapphire for the touchscreen on a 2014 iPhone, but that may be unlikely. The sources themselves note that sapphire ingots are extremely expensive; the covers on the 5s are said to be about five times more expensive than ones using regular materials.
Touch ID may be a logical addition to iPads. Since iPads can sometimes substitute for full-blown computers, fingerprint recognition would make them more secure, and thus more practical. And like the 5s, both iPad models are considered flagship devices.